There are numerous known catalysts for the production of isocyanurate plastics. However, it has never been possible using the known catalysts to solve satisfactorily the problem of shrinkage which is mainly encountered in the case of polyisocyanurate foams having relatively long gel times.
It has surprisingly been found that polyisocyanurate foams which are resistant to shrinkage, even despite long gel times, may be obtained using the hexahydrotriazine carboxylates of the present invention.
The achievement of a high shrinkage stability may also be obtained by the combination of the catalysts of the present invention with other known polyurethane catalysts. Hitherto, in the production of polyisocyanurate foams, it has been possible to add only small quantities of polyurethane catalysts to the isocyanurate catalysts because otherwise shrinkage problems arise. The combination of polyurethane catalysts with the catalysts of the present invention enables the reaction to be controlled as required and any desired ratio to be adjusted between cream time and gel time without any shrinkage effects occurring.